[Filebeat] keep track of bytes read when max_bytes exceeded in last line

[liuwenping]

fix this issue #31863

What does this PR do?

When the last line exceeds the maximum number of bytes, the text will be skipped directly, and then EOF will be returned, but the length of discarded bytes will not be returned, which will result in not being recorded in the registry, further causing repeated reading problems

[elasticmachine]

❕ Build Aborted

The PR is not allowed to run in the CI yet

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Start Time: 2022-06-09T04:06:21.150+0000

• Duration: 4 min 29 sec

Steps errors

Expand to view the steps failures

Error signal

• Took 0 min 0 sec . View more details here
• Description: githubApiCall: The REST API call https://api.github.com/orgs/elastic/members/liuwenping return the message : java.lang.Exception: httpRequest: Failure connecting to the service https://api.github.com/orgs/elastic/members/liuwenping : httpRequest: Failure connecting to the service https://api.github.com/orgs/elastic/members/liuwenping : Code: 404Error: {"message":"User does not exist or is not a member of the organization","documentation_url":"https://docs.github.com/rest/reference/orgs#check-organization-membership-for-a-user"}

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• /package : Generate the packages and run the E2E tests.

• /beats-tester : Run the installation tests with beats-tester.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[elasticmachine]

Pinging @elastic/elastic-agent-data-plane (Team:Elastic-Agent-Data-Plane)

[cmacknz]

/test

[cmacknz]

Thanks for following up with a fix!

I double checked that the test isn't flaky anymore locally.

[cmacknz]

The build here seems to be stuck, all the tests have passed. Merging.

https://beats-ci.elastic.co/blue/organizations/jenkins/Beats%2Fbeats/detail/PR-31882/2/pipeline

[elasticmachine]

❕ Build Aborted

Either there was a build timeout or someone aborted the build.

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Start Time: 2022-06-09T14:41:11.188+0000

• Duration: 363 min 40 sec

Test stats 🧪

Test	Results
Failed	0
Passed	22229
Skipped	1935
Total	24164

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• /package : Generate the packages and run the E2E tests.

• /beats-tester : Run the installation tests with beats-tester.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)